1 files changed, 796 insertions, 0 deletions

diff --git a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zvol.c b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zvol.c
new file mode 100644
index 0000000..9aa8b7f
--- /dev/null
+++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zvol.c
@@ -0,0 +1,796 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+/*
+ * Copyright (c) 2006 Pawel Jakub Dawidek <pjd@FreeBSD.org>
+ * All rights reserved.
+ */
+/*
+ * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
+ * Use is subject to license terms.
+ */
+
+#pragma ident	"%Z%%M%	%I%	%E% SMI"
+
+/*
+ * ZFS volume emulation driver.
+ *
+ * Makes a DMU object look like a volume of arbitrary size, up to 2^64 bytes.
+ * Volumes are accessed through the symbolic links named:
+ *
+ * /dev/zvol/dsk/<pool_name>/<dataset_name>
+ * /dev/zvol/rdsk/<pool_name>/<dataset_name>
+ *
+ * These links are created by the ZFS-specific devfsadm link generator.
+ * Volumes are persistent through reboot.  No user command needs to be
+ * run before opening and using a device.
+ */
+
+#include <sys/param.h>
+#include <sys/kernel.h>
+#include <sys/errno.h>
+#include <sys/uio.h>
+#include <sys/bio.h>
+#include <sys/kmem.h>
+#include <sys/conf.h>
+#include <sys/cmn_err.h>
+#include <sys/stat.h>
+#include <sys/zap.h>
+#include <sys/spa.h>
+#include <sys/zio.h>
+#include <sys/dsl_prop.h>
+#include <sys/byteorder.h>
+#include <sys/dirent.h>
+#include <sys/fs/zfs.h>
+#include <sys/zfs_ioctl.h>
+#include <sys/zil.h>
+#include <sys/refcount.h>
+#include <sys/zfs_znode.h>
+#include <sys/zfs_rlock.h>
+#include <geom/geom.h>
+
+#include "zfs_namecheck.h"
+
+struct g_class zfs_zvol_class = {
+	.name = "ZFS::ZVOL",
+	.version = G_VERSION,
+};
+
+DECLARE_GEOM_CLASS(zfs_zvol_class, zfs_zvol);
+
+#define	ZVOL_OBJ		1ULL
+#define	ZVOL_ZAP_OBJ		2ULL
+
+static uint32_t zvol_minors;
+
+/*
+ * The in-core state of each volume.
+ */
+typedef struct zvol_state {
+	char		zv_name[MAXPATHLEN]; /* pool/dd name */
+	uint64_t	zv_volsize;	/* amount of space we advertise */
+	uint64_t	zv_volblocksize; /* volume block size */
+	struct g_provider *zv_provider;	/* GEOM provider */
+	uint8_t		zv_min_bs;	/* minimum addressable block shift */
+	uint8_t		zv_readonly;	/* hard readonly; like write-protect */
+	objset_t	*zv_objset;	/* objset handle */
+	uint32_t	zv_mode;	/* DS_MODE_* flags at open time */
+	uint32_t	zv_total_opens;	/* total open count */
+	zilog_t		*zv_zilog;	/* ZIL handle */
+	uint64_t	zv_txg_assign;	/* txg to assign during ZIL replay */
+	znode_t		zv_znode;	/* for range locking */
+	int		zv_state;
+	struct bio_queue_head zv_queue;
+	struct mtx	zv_queue_mtx;	/* zv_queue mutex */
+} zvol_state_t;
+
+/*
+ * zvol maximum transfer in one DMU tx.
+ */
+int zvol_maxphys = DMU_MAX_ACCESS/2;
+
+static int zvol_get_data(void *arg, lr_write_t *lr, char *buf, zio_t *zio);
+
+int
+zvol_check_volsize(uint64_t volsize, uint64_t blocksize)
+{
+	if (volsize == 0)
+		return (EINVAL);
+
+	if (volsize % blocksize != 0)
+		return (EINVAL);
+
+#ifdef _ILP32
+	if (volsize - 1 > SPEC_MAXOFFSET_T)
+		return (EOVERFLOW);
+#endif
+	return (0);
+}
+
+int
+zvol_check_volblocksize(uint64_t volblocksize)
+{
+	if (volblocksize < SPA_MINBLOCKSIZE ||
+	    volblocksize > SPA_MAXBLOCKSIZE ||
+	    !ISP2(volblocksize))
+		return (EDOM);
+
+	return (0);
+}
+
+static void
+zvol_readonly_changed_cb(void *arg, uint64_t newval)
+{
+	zvol_state_t *zv = arg;
+
+	zv->zv_readonly = (uint8_t)newval;
+}
+
+int
+zvol_get_stats(objset_t *os, nvlist_t *nv)
+{
+	int error;
+	dmu_object_info_t doi;
+	uint64_t val;
+
+
+	error = zap_lookup(os, ZVOL_ZAP_OBJ, "size", 8, 1, &val);
+	if (error)
+		return (error);
+
+	dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_VOLSIZE, val);
+
+	error = dmu_object_info(os, ZVOL_OBJ, &doi);
+
+	if (error == 0) {
+		dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_VOLBLOCKSIZE,
+		    doi.doi_data_block_size);
+	}
+
+	return (error);
+}
+
+static zvol_state_t *
+zvol_minor_lookup(const char *name)
+{
+	struct g_provider *pp;
+	struct g_geom *gp;
+
+	g_topology_assert();
+
+	LIST_FOREACH(gp, &zfs_zvol_class.geom, geom) {
+		LIST_FOREACH(pp, &gp->provider, provider) {
+			if (strcmp(pp->name + sizeof(ZVOL_DEV_DIR), name) == 0)
+				return (pp->private);
+		}
+	}
+
+	return (NULL);
+}
+
+static int
+zvol_access(struct g_provider *pp, int acr, int acw, int ace)
+{
+	zvol_state_t *zv;
+
+	g_topology_assert();
+
+	zv = pp->private;
+	if (zv == NULL) {
+		if (acr <= 0 && acw <= 0 && ace <= 0)
+			return (0);
+		return (pp->error);
+	}
+
+	ASSERT(zv->zv_objset != NULL);
+
+	if (acw > 0 && (zv->zv_readonly || (zv->zv_mode & DS_MODE_READONLY)))
+		return (EROFS);
+
+	zv->zv_total_opens += acr + acw + ace;
+
+	return (0);
+}
+
+/*
+ * zvol_log_write() handles synchronous writes using TX_WRITE ZIL transactions.
+ *
+ * We store data in the log buffers if it's small enough.
+ * Otherwise we will later flush the data out via dmu_sync().
+ */
+ssize_t zvol_immediate_write_sz = 32768;
+
+static void
+zvol_log_write(zvol_state_t *zv, dmu_tx_t *tx, offset_t off, ssize_t len)
+{
+	uint32_t blocksize = zv->zv_volblocksize;
+	lr_write_t *lr;
+
+	while (len) {
+		ssize_t nbytes = MIN(len, blocksize - P2PHASE(off, blocksize));
+		itx_t *itx = zil_itx_create(TX_WRITE, sizeof (*lr));
+
+		itx->itx_wr_state =
+		    len > zvol_immediate_write_sz ?  WR_INDIRECT : WR_NEED_COPY;
+		itx->itx_private = zv;
+		lr = (lr_write_t *)&itx->itx_lr;
+		lr->lr_foid = ZVOL_OBJ;
+		lr->lr_offset = off;
+		lr->lr_length = nbytes;
+		lr->lr_blkoff = off - P2ALIGN_TYPED(off, blocksize, uint64_t);
+		BP_ZERO(&lr->lr_blkptr);
+
+		(void) zil_itx_assign(zv->zv_zilog, itx, tx);
+		len -= nbytes;
+		off += nbytes;
+	}
+}
+
+static void
+zvol_start(struct bio *bp)
+{
+	zvol_state_t *zv;
+
+	switch (bp->bio_cmd) {
+	case BIO_READ:
+	case BIO_WRITE:
+	case BIO_FLUSH:
+		zv = bp->bio_to->private;
+		ASSERT(zv != NULL);
+		mtx_lock(&zv->zv_queue_mtx);
+		bioq_insert_tail(&zv->zv_queue, bp);
+		wakeup_one(&zv->zv_queue);
+		mtx_unlock(&zv->zv_queue_mtx);
+		break;
+	case BIO_DELETE:
+	case BIO_GETATTR:
+	default:
+		g_io_deliver(bp, EOPNOTSUPP);
+		break;
+	}
+}
+
+static void
+zvol_serve_one(zvol_state_t *zv, struct bio *bp)
+{
+	uint64_t off, volsize;
+	size_t size, resid;
+	char *addr;
+	objset_t *os;
+	rl_t *rl;
+	int error = 0;
+	boolean_t reading;
+
+	off = bp->bio_offset;
+	volsize = zv->zv_volsize;
+
+	os = zv->zv_objset;
+	ASSERT(os != NULL);
+
+	addr = bp->bio_data;
+	resid = bp->bio_length;
+
+	error = 0;
+
+	/*
+	 * There must be no buffer changes when doing a dmu_sync() because
+	 * we can't change the data whilst calculating the checksum.
+	 * A better approach than a per zvol rwlock would be to lock ranges.
+	 */
+	reading = (bp->bio_cmd == BIO_READ);
+	rl = zfs_range_lock(&zv->zv_znode, off, resid,
+	    reading ? RL_READER : RL_WRITER);
+
+	while (resid != 0 && off < volsize) {
+
+		size = MIN(resid, zvol_maxphys); /* zvol_maxphys per tx */
+
+		if (size > volsize - off)	/* don't write past the end */
+			size = volsize - off;
+
+		if (reading) {
+			error = dmu_read(os, ZVOL_OBJ, off, size, addr);
+		} else {
+			dmu_tx_t *tx = dmu_tx_create(os);
+			dmu_tx_hold_write(tx, ZVOL_OBJ, off, size);
+			error = dmu_tx_assign(tx, TXG_WAIT);
+			if (error) {
+				dmu_tx_abort(tx);
+			} else {
+				dmu_write(os, ZVOL_OBJ, off, size, addr, tx);
+				zvol_log_write(zv, tx, off, size);
+				dmu_tx_commit(tx);
+			}
+		}
+		if (error)
+			break;
+		off += size;
+		addr += size;
+		resid -= size;
+	}
+	zfs_range_unlock(rl);
+
+	bp->bio_completed = bp->bio_length - resid;
+	if (bp->bio_completed < bp->bio_length)
+		bp->bio_error = (off > volsize ? EINVAL : error);
+
+	/*
+	 * XXX: We are devilering here?
+	 * Looks like I don't understand something here, but I was sure it was
+	 * an async request.
+	 */
+	g_io_deliver(bp, bp->bio_error);
+}
+
+static void
+zvol_worker(void *arg)
+{
+	zvol_state_t *zv;
+	struct bio *bp;
+
+	zv = arg;
+	for (;;) {
+		mtx_lock(&zv->zv_queue_mtx);
+		bp = bioq_takefirst(&zv->zv_queue);
+		if (bp == NULL) {
+			if (zv->zv_state == 1) {
+				zv->zv_state = 2;
+				wakeup(&zv->zv_state);
+				mtx_unlock(&zv->zv_queue_mtx);
+				kthread_exit(0);
+			}
+			msleep(&zv->zv_queue, &zv->zv_queue_mtx, PRIBIO | PDROP,
+			    "zvol:io", 0);
+			continue;
+		}
+		mtx_unlock(&zv->zv_queue_mtx);
+		if (bp->bio_cmd == BIO_FLUSH) {
+			zil_commit(zv->zv_zilog, UINT64_MAX, ZVOL_OBJ);
+			g_io_deliver(bp, 0);
+		} else {
+			zvol_serve_one(zv, bp);
+		}
+	}
+}
+
+void
+zvol_create_cb(objset_t *os, void *arg, dmu_tx_t *tx)
+{
+	zfs_create_data_t *zc = arg;
+	int error;
+	uint64_t volblocksize, volsize;
+
+	VERIFY(nvlist_lookup_uint64(zc->zc_props,
+	    zfs_prop_to_name(ZFS_PROP_VOLSIZE), &volsize) == 0);
+	if (nvlist_lookup_uint64(zc->zc_props,
+	    zfs_prop_to_name(ZFS_PROP_VOLBLOCKSIZE), &volblocksize) != 0)
+		volblocksize = zfs_prop_default_numeric(ZFS_PROP_VOLBLOCKSIZE);
+
+	/*
+	 * These properites must be removed from the list so the generic
+	 * property setting step won't apply to them.
+	 */
+	VERIFY(nvlist_remove_all(zc->zc_props,
+	    zfs_prop_to_name(ZFS_PROP_VOLSIZE)) == 0);
+	(void) nvlist_remove_all(zc->zc_props,
+	    zfs_prop_to_name(ZFS_PROP_VOLBLOCKSIZE));
+
+	error = dmu_object_claim(os, ZVOL_OBJ, DMU_OT_ZVOL, volblocksize,
+	    DMU_OT_NONE, 0, tx);
+	ASSERT(error == 0);
+
+	error = zap_create_claim(os, ZVOL_ZAP_OBJ, DMU_OT_ZVOL_PROP,
+	    DMU_OT_NONE, 0, tx);
+	ASSERT(error == 0);
+
+	error = zap_update(os, ZVOL_ZAP_OBJ, "size", 8, 1, &volsize, tx);
+	ASSERT(error == 0);
+}
+
+/*
+ * Replay a TX_WRITE ZIL transaction that didn't get committed
+ * after a system failure
+ */
+static int
+zvol_replay_write(zvol_state_t *zv, lr_write_t *lr, boolean_t byteswap)
+{
+	objset_t *os = zv->zv_objset;
+	char *data = (char *)(lr + 1);	/* data follows lr_write_t */
+	uint64_t off = lr->lr_offset;
+	uint64_t len = lr->lr_length;
+	dmu_tx_t *tx;
+	int error;
+
+	if (byteswap)
+		byteswap_uint64_array(lr, sizeof (*lr));
+
+	tx = dmu_tx_create(os);
+	dmu_tx_hold_write(tx, ZVOL_OBJ, off, len);
+	error = dmu_tx_assign(tx, zv->zv_txg_assign);
+	if (error) {
+		dmu_tx_abort(tx);
+	} else {
+		dmu_write(os, ZVOL_OBJ, off, len, data, tx);
+		dmu_tx_commit(tx);
+	}
+
+	return (error);
+}
+
+/* ARGSUSED */
+static int
+zvol_replay_err(zvol_state_t *zv, lr_t *lr, boolean_t byteswap)
+{
+	return (ENOTSUP);
+}
+
+/*
+ * Callback vectors for replaying records.
+ * Only TX_WRITE is needed for zvol.
+ */
+zil_replay_func_t *zvol_replay_vector[TX_MAX_TYPE] = {
+	zvol_replay_err,	/* 0 no such transaction type */
+	zvol_replay_err,	/* TX_CREATE */
+	zvol_replay_err,	/* TX_MKDIR */
+	zvol_replay_err,	/* TX_MKXATTR */
+	zvol_replay_err,	/* TX_SYMLINK */
+	zvol_replay_err,	/* TX_REMOVE */
+	zvol_replay_err,	/* TX_RMDIR */
+	zvol_replay_err,	/* TX_LINK */
+	zvol_replay_err,	/* TX_RENAME */
+	zvol_replay_write,	/* TX_WRITE */
+	zvol_replay_err,	/* TX_TRUNCATE */
+	zvol_replay_err,	/* TX_SETATTR */
+	zvol_replay_err,	/* TX_ACL */
+};
+
+/*
+ * Create a minor node for the specified volume.
+ */
+int
+zvol_create_minor(const char *name, dev_t dev)
+{
+	struct g_provider *pp;
+	struct g_geom *gp;
+	zvol_state_t *zv;
+	objset_t *os;
+	dmu_object_info_t doi;
+	uint64_t volsize;
+	int ds_mode = DS_MODE_PRIMARY;
+	int error;
+
+	DROP_GIANT();
+	g_topology_lock();
+
+	if ((zv = zvol_minor_lookup(name)) != NULL) {
+		error = EEXIST;
+		goto end;
+	}
+
+	if (strchr(name, '@') != 0)
+		ds_mode |= DS_MODE_READONLY;
+
+	error = dmu_objset_open(name, DMU_OST_ZVOL, ds_mode, &os);
+	if (error)
+		goto end;
+
+	g_topology_unlock();
+	PICKUP_GIANT();
+	error = zap_lookup(os, ZVOL_ZAP_OBJ, "size", 8, 1, &volsize);
+	DROP_GIANT();
+	g_topology_lock();
+	if (error) {
+		dmu_objset_close(os);
+		goto end;
+	}
+
+	gp = g_new_geomf(&zfs_zvol_class, "zfs::zvol::%s", name);
+	gp->start = zvol_start;
+	gp->access = zvol_access;
+	pp = g_new_providerf(gp, "%s/%s", ZVOL_DEV_DIR, name);
+	pp->mediasize = volsize;
+	pp->sectorsize = DEV_BSIZE;
+
+	zv = kmem_zalloc(sizeof(*zv), KM_SLEEP);
+	(void) strcpy(zv->zv_name, name);
+	zv->zv_min_bs = DEV_BSHIFT;
+	zv->zv_provider = pp;
+	zv->zv_volsize = pp->mediasize;
+	zv->zv_objset = os;
+	zv->zv_mode = ds_mode;
+	zv->zv_zilog = zil_open(os, zvol_get_data);
+	mutex_init(&zv->zv_znode.z_range_lock, NULL, MUTEX_DEFAULT, NULL);
+	avl_create(&zv->zv_znode.z_range_avl, zfs_range_compare,
+	    sizeof (rl_t), offsetof(rl_t, r_node));
+
+
+	/* get and cache the blocksize */
+	error = dmu_object_info(os, ZVOL_OBJ, &doi);
+	ASSERT(error == 0);
+	zv->zv_volblocksize = doi.doi_data_block_size;
+
+	zil_replay(os, zv, &zv->zv_txg_assign, zvol_replay_vector);
+
+	/* XXX this should handle the possible i/o error */
+	VERIFY(dsl_prop_register(dmu_objset_ds(zv->zv_objset),
+	    "readonly", zvol_readonly_changed_cb, zv) == 0);
+
+	pp->private = zv;
+	g_error_provider(pp, 0);
+
+	bioq_init(&zv->zv_queue);
+	mtx_init(&zv->zv_queue_mtx, "zvol", NULL, MTX_DEF);
+	zv->zv_state = 0;
+	kthread_create(zvol_worker, zv, NULL, 0, 0, "zvol:worker %s", pp->name);
+
+	zvol_minors++;
+end:
+	g_topology_unlock();
+	PICKUP_GIANT();
+
+	return (error);
+}
+
+/*
+ * Remove minor node for the specified volume.
+ */
+int
+zvol_remove_minor(const char *name)
+{
+	struct g_provider *pp;
+	zvol_state_t *zv;
+	int error = 0;
+
+	DROP_GIANT();
+	g_topology_lock();
+
+	if ((zv = zvol_minor_lookup(name)) == NULL) {
+		error = ENXIO;
+		goto end;
+	}
+
+	if (zv->zv_total_opens != 0) {
+		error = EBUSY;
+		goto end;
+	}
+
+	VERIFY(dsl_prop_unregister(dmu_objset_ds(zv->zv_objset),
+	    "readonly", zvol_readonly_changed_cb, zv) == 0);
+
+	mtx_lock(&zv->zv_queue_mtx);
+	zv->zv_state = 1;
+	wakeup_one(&zv->zv_queue);
+	while (zv->zv_state != 2)
+		msleep(&zv->zv_state, &zv->zv_queue_mtx, 0, "zvol:w", 0);
+	mtx_unlock(&zv->zv_queue_mtx);
+	mtx_destroy(&zv->zv_queue_mtx);
+
+	pp = zv->zv_provider;
+	pp->private = NULL;
+	g_wither_geom(pp->geom, ENXIO);
+
+	zil_close(zv->zv_zilog);
+	zv->zv_zilog = NULL;
+	dmu_objset_close(zv->zv_objset);
+	zv->zv_objset = NULL;
+	avl_destroy(&zv->zv_znode.z_range_avl);
+	mutex_destroy(&zv->zv_znode.z_range_lock);
+
+	kmem_free(zv, sizeof(*zv));
+
+	zvol_minors--;
+end:
+	g_topology_unlock();
+	PICKUP_GIANT();
+
+	return (error);
+}
+
+int
+zvol_set_volsize(const char *name, dev_t dev, uint64_t volsize)
+{
+	zvol_state_t *zv;
+	dmu_tx_t *tx;
+	int error;
+	dmu_object_info_t doi;
+
+	DROP_GIANT();
+	g_topology_lock();
+
+	if ((zv = zvol_minor_lookup(name)) == NULL) {
+		error = ENXIO;
+		goto end;
+	}
+
+	if ((error = dmu_object_info(zv->zv_objset, ZVOL_OBJ, &doi)) != 0 ||
+	    (error = zvol_check_volsize(volsize,
+	    doi.doi_data_block_size)) != 0) {
+		goto end;
+	}
+
+	if (zv->zv_readonly || (zv->zv_mode & DS_MODE_READONLY)) {
+		error = EROFS;
+		goto end;
+	}
+
+	tx = dmu_tx_create(zv->zv_objset);
+	dmu_tx_hold_zap(tx, ZVOL_ZAP_OBJ, TRUE, NULL);
+	dmu_tx_hold_free(tx, ZVOL_OBJ, volsize, DMU_OBJECT_END);
+	error = dmu_tx_assign(tx, TXG_WAIT);
+	if (error) {
+		dmu_tx_abort(tx);
+		goto end;
+	}
+
+	error = zap_update(zv->zv_objset, ZVOL_ZAP_OBJ, "size", 8, 1,
+	    &volsize, tx);
+	if (error == 0) {
+		error = dmu_free_range(zv->zv_objset, ZVOL_OBJ, volsize,
+		    DMU_OBJECT_END, tx);
+	}
+
+	dmu_tx_commit(tx);
+
+	if (error == 0) {
+		zv->zv_volsize = volsize;
+		zv->zv_provider->mediasize = volsize;	/* XXX: Not supported. */
+	}
+end:
+	g_topology_unlock();
+	PICKUP_GIANT();
+
+	return (error);
+}
+
+int
+zvol_set_volblocksize(const char *name, uint64_t volblocksize)
+{
+	zvol_state_t *zv;
+	dmu_tx_t *tx;
+	int error;
+
+	DROP_GIANT();
+	g_topology_lock();
+
+	if ((zv = zvol_minor_lookup(name)) == NULL) {
+		error = ENXIO;
+		goto end;
+	}
+
+	if (zv->zv_readonly || (zv->zv_mode & DS_MODE_READONLY)) {
+		error = EROFS;
+		goto end;
+	}
+
+	tx = dmu_tx_create(zv->zv_objset);
+	dmu_tx_hold_bonus(tx, ZVOL_OBJ);
+	error = dmu_tx_assign(tx, TXG_WAIT);
+	if (error) {
+		dmu_tx_abort(tx);
+	} else {
+		error = dmu_object_set_blocksize(zv->zv_objset, ZVOL_OBJ,
+		    volblocksize, 0, tx);
+		if (error == ENOTSUP)
+			error = EBUSY;
+		dmu_tx_commit(tx);
+		/* XXX: Not supported. */
+#if 0
+		if (error == 0)
+			zv->zv_provider->sectorsize = zc->zc_volblocksize;
+#endif
+	}
+end:
+	g_topology_unlock();
+	PICKUP_GIANT();
+
+	return (error);
+}
+
+void
+zvol_get_done(dmu_buf_t *db, void *vzgd)
+{
+	zgd_t *zgd = (zgd_t *)vzgd;
+	rl_t *rl = zgd->zgd_rl;
+
+	dmu_buf_rele(db, vzgd);
+	zfs_range_unlock(rl);
+	zil_add_vdev(zgd->zgd_zilog, DVA_GET_VDEV(BP_IDENTITY(zgd->zgd_bp)));
+	kmem_free(zgd, sizeof (zgd_t));
+}
+
+/*
+ * Get data to generate a TX_WRITE intent log record.
+ */
+static int
+zvol_get_data(void *arg, lr_write_t *lr, char *buf, zio_t *zio)
+{
+	zvol_state_t *zv = arg;
+	objset_t *os = zv->zv_objset;
+	dmu_buf_t *db;
+	rl_t *rl;
+	zgd_t *zgd;
+	uint64_t boff; 			/* block starting offset */
+	int dlen = lr->lr_length;	/* length of user data */
+	int error;
+
+	ASSERT(zio);
+	ASSERT(dlen != 0);
+
+	/*
+	 * Write records come in two flavors: immediate and indirect.
+	 * For small writes it's cheaper to store the data with the
+	 * log record (immediate); for large writes it's cheaper to
+	 * sync the data and get a pointer to it (indirect) so that
+	 * we don't have to write the data twice.
+	 */
+	if (buf != NULL) /* immediate write */
+		return (dmu_read(os, ZVOL_OBJ, lr->lr_offset, dlen, buf));
+
+	zgd = (zgd_t *)kmem_alloc(sizeof (zgd_t), KM_SLEEP);
+	zgd->zgd_zilog = zv->zv_zilog;
+	zgd->zgd_bp = &lr->lr_blkptr;
+
+	/*
+	 * Lock the range of the block to ensure that when the data is
+	 * written out and it's checksum is being calculated that no other
+	 * thread can change the block.
+	 */
+	boff = P2ALIGN_TYPED(lr->lr_offset, zv->zv_volblocksize, uint64_t);
+	rl = zfs_range_lock(&zv->zv_znode, boff, zv->zv_volblocksize,
+	    RL_READER);
+	zgd->zgd_rl = rl;
+
+	VERIFY(0 == dmu_buf_hold(os, ZVOL_OBJ, lr->lr_offset, zgd, &db));
+	error = dmu_sync(zio, db, &lr->lr_blkptr,
+	    lr->lr_common.lrc_txg, zvol_get_done, zgd);
+	if (error == 0)
+		zil_add_vdev(zv->zv_zilog,
+		    DVA_GET_VDEV(BP_IDENTITY(&lr->lr_blkptr)));
+	/*
+	 * If we get EINPROGRESS, then we need to wait for a
+	 * write IO initiated by dmu_sync() to complete before
+	 * we can release this dbuf.  We will finish everything
+	 * up in the zvol_get_done() callback.
+	 */
+	if (error == EINPROGRESS)
+		return (0);
+	dmu_buf_rele(db, zgd);
+	zfs_range_unlock(rl);
+	kmem_free(zgd, sizeof (zgd_t));
+	return (error);
+}
+
+int
+zvol_busy(void)
+{
+	return (zvol_minors != 0);
+}
+
+void
+zvol_init(void)
+{
+	ZFS_LOG(1, "ZVOL Initialized.");
+}
+
+void
+zvol_fini(void)
+{
+	ZFS_LOG(1, "ZVOL Deinitialized.");
+}